A) Field of the Invention
The present invention relates to a semiconductor device manufacture method, and more particularly to a method of manufacturing a semiconductor device wherein a conductive film or insulating film is formed on a substrate, this film is chemically and mechanically polished, and thereafter the polished surface is washed and cleaned.
B) Description of the Related Art
In order to realize finer patterning, recent miniaturization techniques and lithography techniques adopt a process of planarizing the surface of a semiconductor wafer to be processed. Planarizing techniques called chemical mechanical polishing (CMP) have been often applied to the planarizing processes. CMP techniques will be briefly described.
A polishing pad (polishing cloth) is fixed to a polishing platen, and slurry is supplied onto the polishing pad. A semiconductor wafer to be polished is pushed against the polishing pad to polish the semiconductor wafer while both the polishing pad and semiconductor wafer are rotated.
Slurry is added with abrasive grains (powders) mainly made of silicon oxide and various chemicals such as polishing accelerator. These abrasive grains and various chemicals often contain contaminated substances which may cause some trouble during the manufacture of semiconductor devices. In order to remove contaminated substances, washing and cleaning processes are executed after CMP. The contaminated substances often adhere to the abrasive grains and foreign matters (fine particles) that are generated during CMP. If foreign matters are left on the surface of a semiconductor wafer, these foreign matters may cause some trouble during the succeeding manufacture processes, which may become a factor of low manufacture yield. One of important objects of the washing and cleaning process is to remove abrasive grains and foreign matters left on the surface of a semiconductor wafer.
Alkali liquid is used as the washing and cleaning liquid for removing foreign matters. Acid solution is used as the washing and cleaning liquid for removing contaminated elements. Washing and cleaning liquid whose liquid performance and additive chemical liquid are adjusted is also known which is used for removing both foreign matters and contaminated elements. In order to prevent a metal film of copper or the like from being corroded during washing and cleaning, anticorrosive is added to washing and cleaning liquid and this solution is used for washing and cleaning a semiconductor wafer while the surface of a metal film is protected. Japanese Patent Laid-open Publication No. HEI-11-40526 discloses the techniques in which the surface of a semiconductor wafer after CMP is washed and cleaned with washing and cleaning liquid added with anticorrosive of benzotriazole (BTA).
Slurry which contains anticorrosive is generally used for polishing a copper layer in order to adjust a removal rate for copper and prevent corrosion of copper. Also known is slurry which does not contain anticorrosive in order to set removal rates for copper and silicon oxide near each other (refer to Japanese Patent Laid-open Publication No. 2001-196336).
Evaluation experiments made by the present inventors will be described. A silicon oxide film was formed on the surface of an eight-inch silicon wafer by plasma enhanced-chemical vapor deposition (PE-CVD). Slurry was produced by adding pure water to silicon oxide abrasive grains and adding alkaline solution (potassium hydroxide solution) to adjust its pH to 8 or higher. By using this slurry, the silicon oxide film was polished. Even after this polishing, the silicon oxide film is left on the whole surface of the silicon wafer.
After the polishing, the surface of the silicon wafer was washed and cleaned with alkali washing and cleaning liquid whose pH was adjusted to 10 or higher by adding alkali solution, anticorrosive and pure water. Thereafter, the surface of the silicon wafer was washed and cleaned by acid washing and cleaning liquid whose pH was adjusted to 5 or lower by adding organic acid. The surface of the silicon wafer was dried with a spin drier.
The attachment conditions of foreign matters on the silicon wafer surface after washing and cleaning were observed with a defect inspection apparatus. In this observation, foreign matters having a size equal to about 0.1 μm or larger are counted. Ninety thousand foreign matters existed on the silicon oxide film formed on the silicon wafer surface. It is therefore difficult to remove foreign matters sufficiently by using the conventional washing and cleaning method.
As described in the above-cited Japanese Patent Laid-open Publication No. HEI-11-40526, copper of a copper wiring layer formed by a damascene method can be prevented from being corroded if anticorrosive is added to washing and cleaning solution. There is no description of the foreign matter removal in this Publication.